This makes it C99. If you aren't compiling in C99 mode, you cannot put the keyword int there. It has to be like this:

Code:

int i3;
...stuff...
for ( i3 = 0; i < N; i3++) {

You aren't compiling in C99 mode, because if you were, it wouldn't tell you "outside of C99 mode". Also, in case you don't know, were you do do the first method, and compile in C99 mode, the variable "i3" ceases to exist when the loop ends.

if im not compiling on C99 mode is there any way to compile on c99 mode using dev-cpp?

as of now - no. Dev-Cpp only supports some c99 features, like most compilers. Your best bet would be to follow salem an Quzah's advice an make it C90, what most compilers support. For compiler specific info you can check this out.